Technical Field
Embodiments of the present disclosure relate to a fixing device to fix a toner image on a recording medium, and an image forming apparatus including the fixing device.
Description of the Related Art
Currently, regarding image forming apparatuses such as printers, copiers, and facsimile machines, demands for speedup and extended operational life are increasing.
In image forming apparatuses, unfixed toner images are formed, either directly or via a transfer medium, on recording media through image forming process employing electrophotography, electrostatic recording, magnetic recording, or the like. The recording media include recording sheets, printing paper, photosensitive sheets, and electrostatic recording sheets. There are various types of fixing devices to fix unfixed toner images. Widely used fixing device type is contact-heating type, such as roller heating, film heating, and electromagnetic induction heating.
There are fixing devices in which an endless fixing belt having a low thermal capacity is directly heated without using a heat conductor made of metal, to cope with speed up of image forming apparatuses. In such fixing devices, in heating the fixing belt, the speed of temperature rise thereof is faster. Accordingly, there is a risk that, due to control failure of some kind, the temperature of the fixing belt rises abruptly and exceeds a predetermined temperature (e.g., a highest tolerable temperature). Therefore, fixing devices are generally provided with a safeguard to stop heating in the case of such an abrupt temperature rise.